Target alignment on the LIL laser facility

Abstract

One way to achieve fusion in laboratory consists in heating and compressing, by using a laser, a capsule containing a deuterium - tritium mix. Achievement of such a project can be obtained only through the development of a new generation of laser facilities. With this end in view, CEA is developing the "Laser Mega-Joule" (LMJ), a facility made of 240 laser lines. The "Ligne d'Intégration Laser" (LIL) is a prototype of the LMJ made of a four laser lines assembly. Presently operational, it must permit the validation of the technological choices that have been made. Particular attention must be given in the achievement of the alignment of the target compared with the laser beams: it must be positioned at the center of the target chamber with a precision better than fifty micrometers rms. The quality of this alignment must be guaranteed in order to ensure the success of the physics experiments performed on the facility. We are presenting the device that has been devised to reach this objective: the "Système de Visualisation de Cible" (SYVIC) or target viewing system. This device is made of two optical visors set on the target chamber, associated with a complicated three-dimensional reconstruction algorithm. It permits to position an object at the center of the chamber, rapidly and with the required orientation. It also makes possible the alignment of all the plasma diagnostics, mounted on the chamber wall in order to study the plasma created by the laser-matter interaction. The first plasma experiment using the SYVIC alignment device took place at the beginning of 2007 with a specific target. Doing so we qualified the accuracy of this device and its implementation on LIL.